Takahiro Onimaru

Superconductivity and Structural Phase Transitions in Caged Compounds RT2Zn20 (R = La, Pr, T = Ru, Ir)

Electrical resistivity ρ, specific heat C , magnetization M measurements are reported on four compounds, LaRu 2 Zn 20 , PrRu 2 Zn 20 , LaIr 2 Zn 20 , and PrIr 2 Zn 20 , which crystallize in a cubic CeCr 2 Al 20 -type structure. LaRu 2 Zn 20 , LaIr 2 Zn 20 , and PrIr 2 Zn 20 show superconducting transitions at T C = 0.2, 0.6, and ∼0.05 K, respectively, whereas PrRu 2 Zn 20 remains a normal state down to 0.04 K. This is the first observation of superconductivity in the family of RT 2 X 20 (T = transition metal; X = Al and Zn). Furthermore, structural phase transitions manifest themselves at T s = 150, 138, and 200 K for LaRu 2 Zn 20 , PrRu 2 Zn 20 , and LaIr 2 Zn 20 , respectively. No magnetic transition is found in PrRu 2 Zn 20 and PrIr 2 Zn 20 down to 1.8 K. On cooling PrIr 2 Zn 20 below 2 K, the specific heat divided by temperature, C / T , continuously increases and reaches 5 J/(K 2 ·mol) at 0.4 K, suggesting that Pr 4 f 2 electrons are involved in the heavy-fermion state, as observed in a related compo...

Neutron Powder Diffraction on Ce 11B 2C 2 and Nd 11B 2C 2: A New Model for the Tetragonal Crystal Structure

Crystal structures of CeB 2 C 2 and NdB 2 C 2 were investigated by means of neutron powder diffraction using 11 B enriched samples. Diffraction patterns of Ce 11 B 2 C 2 and Nd 11 B 2 C 2 are very similar to each other, and Rietveld analyses reveal that the crystal structure belongs to a symmetry group of tetragonal P 4/ m b m , where the rare earth atoms occupy 2( a ) sites and the B and C atoms occupy two 4( h ) sites with different positional parameters. The newly determined structure differs from previously reported ones with P 4/ m b m and \(P{\overline 4}2c\) mainly in the site positions occupied by the B and C atoms. The B and C atoms form network planes consisting of non-regular squares and octagons.

Observation of modulated quadrupolar structures in PrPb3.

Neutron diffraction measurements have been performed on the cubic compound PrPb(3) in a [001] magnetic field to examine the quadrupolar ordering. Antiferromagnetic components with q = (1/2 +/- delta 1/2 0), (1/2 1/2 +/- delta 0) (delta approximately 1/8) are observed below the transition temperature T(Q) (0.4 K at H = 0) whose amplitudes vary linear with H and vanish at zero field, providing the first evidence for a modulated quadrupolar phase. For H < 1 T, a nonsquare modulated state persists even below 100 mK suggesting quadrupole moments associated with a Tau(3) doublet ground state to be partially quenched by hybridization with conduction electrons.

Simultaneous superconducting and antiferroquadrupolar transitions in PrRh2Zn20

Superconducting and antiferroquadrupolar (AFQ) transitions in a Pr-based compound PrRh

Thermoelectric and Magnetic Properties of a Narrow-Gap Semiconductor FeGa3

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Antiferro-Quadrupolar Ordering at the Lowest Temperature and Anisotropic Magnetic Field–Temperature Phase Diagram in the Cage Compound PrIr2Zn20

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Magnetic and Transport Properties of ROs2Al10 (R=Pr, Nd, Sm, and Gd)

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Antiferromagnetic Structure with the Uniaxial Anisotropy in the Tetragonal LaB2C2 Type Compound, NdB2C2.

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Thermoelectric properties of Mn-doped Mg–Sb single crystals

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